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Mark Robertson Professor of Biology
Delta College
Nucleic Acids DNA and RNA
The Role of Nucleic Acids
DNA
DNA polymerase
RNA polymerase RNA
Proteins
Translation(convert RNA to proteins)
Transcription(convert DNA to RNA)
Ribosome
Replication(DNA to 2 x DNA)
Molecular Structure of DNA/RNA
Made of linked nucleotide monomers
Phosphate group Sugar (ribose or deoxyribose) 1 of 5 Bases (cytosine, guanine, adenine, thymine, or uracil)
DNA is a double helix polymer while RNA is a single stranded polymer
Chromosomes composed of DNA wound around proteins (histones) while chromatin is unwound DNA
Replication of DNADNA is “unzipped” by one enzyme and then DNA polymerase moves down both strands and adds free nucleotides (absorbed from diet) to form complementary strands
DNA is now half old/half new (called “semiconservative” replication)
Cell can now divide with duplicate strands of DNA in each daughter cell (forming 46 chromosomes in humans)
Genes on the chromosomes have a “Start” code (TAC) and end with a telomere (repeated “Stop” sequence)
DNA Transcription
DNA stays in the nucleus and is used to make all 3 types of RNA:
mRNA (messenger RNA to move information out of nucleus)
tRNA (transfer RNA, moves amino acids to the ribosome)
rRNA (ribosomal RNA, makes the 2 parts of the ribosomes)
Starts with “unzipping” by an enzyme. A “gene” in the DNA consists of “triplet” sequences and is read by RNA polymerase. The RNA “codons” are attached by RNA polymerase if they fit the triplets. Only one DNA strand is transcribed by RNA polymerase
DNA TranslationNeed a:
blueprint (mRNA) some raw materials (dietary amino acids) some trucks (tRNAs) a factory (ribosomes made from rRNA)
The two ribosome subunits assemble on a mRNA at “start” code of AUG. Each tRNA that has an “anticodon” matching the “codon” on the mRNA is drawn into slots on the ribosome. When two loaded tRNAs are pulled into the ribosome and their amino acids are side-‐by-‐sedu, they are linked together (by a peptide bond) until the ribosome reaches a stop code
TAC-CAG-TGC-TAG-GTC-TCG-ATT Gene
Let’s PracticeCan you produce a complementary DNA strand?
Can you translate the mRNA codons into a protein?Please transcribe the DNA into mRNA codons.
How did the “wobble theory” affect potential mutations?
Transcription/Translation Summary Diagram
Potential Journal Critique Topics?Recombinant DNA and Diseases?
Autosomal Dominant Disorders (like Dwarfism and Huntington’s Chorea)?
Chromosomal Translocations, Deletions, Insertions, and Inversions?
RNA Based Disorders (ex: Myotonic Dystrophy)?
Monosomy/Trisomy Autosomal Disorders (like Trisomy 21)?
Sex Chromosome Disorders?